From: In vivo continuous evolution of metabolic pathways for chemical production
Type | Selection pressure | Principle | Products | Original yield or titre | Optimised yield or titre | Evolution time, generations | Ref |
---|---|---|---|---|---|---|---|
Natural metabolite production/cell fitness coupling | Hydrogen peroxide | Production of β-carotene as antioxidant to neutralise the oxidative stress of hydrogen peroxide | β-carotene | 6 mg g−1 [dcw] | 18 mg g−1 [dcw] | 40 | [79] |
LB medium | Coupling ATP and lactate production to growth by engineering lactate production route as the sole anaerobic NADH oxidation route | d-lactate | Maximum production: 865 ± 36 mmol l−1 Yield: 86% | Maximum production: 1071 ± 2 mmol l−1 Yield: 93% | 34 | [83] | |
NBS medium with glucose and betaine (optional) | l-lactate | Maximum production: 1228 ± 31 mmol l−1 Yield: 95% | Maximum production: 1314 ± 48 mmol l−1 Yield: 98% | 80 | [85] | ||
Metabolic evolution | NBS or AM1 medium with glucose | Coupling ATP and growth to alanine production and NADH oxidation | l-alanine | Maximum production: 181 mmol l−1 Yield: 81% | Maximum production: 1279 mmol l−1 Yield: 95% | 123 | [86] |
NBS medium with 9% xylose | D(–)-lactate hydrogenase fermentation pathway as the sole fermentative pathway coupled with the growth of strain | Ethanol | ≈ 250 mM | ≈ 950 mM | 38 | [87] | |
NBS or AM1 medium with glucose | Coupling growth and glucose fermentation to NADH oxidisation pathway | Succinate | 108Â mM | 699Â mM | 150 | ||
Malate | 0Â mM | 313Â mM | |||||
Artificial metabolite production/cell fitness coupling | Nickel ion | Riboselector connecting phosphoenolpyruvate to oxaloacetate which is a precursor to lysine | l-lysine | 0.0 g l−1 | 0.6 g l−1 | 12 | [92] |
Sodium dodecyl-sulphate (SDS) for positive selection and colicin E1 for negative selection | Sensor-selector connecting a chemical sensor to a cognate promoting operator controlling selector and tolC toggle switch for reverse selection | Naringenin | 1.69 mg l−1 | 61 mg l−1 | 60a | [90] | |
Glucaric acid | 0.05 mg l−1 | 1.2 mg l−1 | 5a | [90] | |||
Maltose | Maltose hydrolase is coupled to tryptophan sensor and the cell is cultured in a medium with maltose as a sole carbon source to couple cell growth to tryptophan production | l-trytophan | 0.5 mg l−1 OD −1600 | 5 mg l−1 OD −1600 | 12 | [95] | |
N/A | Co-cultivation of auxotroph to couple the growth of secretor strain and sensor strain to amplify the difference in production level. 2-ketoisovalerate auxotroph is used as sensor strain, while lysine auxotroph is used as secretor strain | Isobutanol | 1.8 ± 0.1 g l−1 | 9.4 ± 0.4 g l−1 | N/A | [96] |